The present invention relates generally to the high speed winding of filamentary material onto bobbins or spools to form packages of filamentary material. More particularly, it relates to the handling of man-made filament yarn during the final stages of winding a full package.
The manufacture of man-made or synthetic filament yarns is typically achieved by extruding a molten polymer, such as polyester, polyamide, etc., through hole(s) in a spinneret and then cooling the filament(s) thus formed. Thereafter, the filaments may be gathered together to form a multi-filament yarn and, possibly after further treatment, are wound onto a tube so that a yarn package is formed.
Winding of the yarn is performed mechanically by winders which rotate one or more tubes to wind-up the yarn while traversing the yarn along the tube axis to achieve a uniform thickness of yarn being wound.
A doffing/donning operation (i.e., replacement of the yarn packages with empty tubes on the winder) is often performed manually by an operator who (i) severs the yarn, (ii) stops the rotary drive to the packages, (iii) replaces the packages with empty tubes, (iv) re-establishes the rotary drive between the winder drive head and the tubes, and (v) rethreads the yarn onto the empty tubes. Severing of the filamentary yarn is typically performed with scissors while the inlet of a suction or aspirator gun is held against the yarn at a location above the point of severing. Once the yarn is severed, the trailing end of the yarn is wound onto the yarn package, while the newly formed leading end of the yarn is sucked into the aspirator and fed to a waste collector. The suction gun is then placed onto a holder while the yarn packages are being replaced by empty tubes. When the empty tubes attain full speed, the operator manipulates the suction gun to attach the yarn to the rotating tubes so that this winding operation may begin.
In order to economize such winding operations, it has heretofore been proposed to mechanize the doffing and donning operations to a certain extent by providing a mechanism which automatically severs, aspirates and rethreads the yarn. Exemplary of proposed mechanisms of that type are the disclosures in U.S. Pat. No. 4,023,741 issued to Schar on May 17, 1977; U.S. Pat. No. 4,052,017 issued to Schar on Oct. 4, 1977; and U.S. Pat. No. 4,108,388 issued to Schar on Aug. 22, 1978.
At the end of a winding sequence and after the yarn has been cut, the package spindle is braked to a stop. If the yarn trailing end is not tightly wound on the package it may unravel to some extent as the package decelerates to a stop. The tendency for the yarn to unravel may be heightened in cases where the package is surface-driven by a drive roll on a winder head. That is, as the winder head lifts from the filled package, the yarn trailing end is subjected to the turbulent wind created by the still-rotating drive roll and/or grooved guide roll. Such an unwound end can pose problems as it whips about against the decelerating package because it may tend to impact against and damage the exposed windings of yarn on the package.
It has been heretofore proposed in U.S. Pat. No. 4,384,689 to alleviate this problem by displacing the yarn trailing end from the traverse guide and grooved roll of the winder just prior to termination of the winding sequence and transferring such end to a winding guide which holds this yarn trailing end against traversing movement along the axis of the package. As a result, the yarn trailing end is wound in close order upon the package whereby subsequent unraveling of the trailing end is effectively resisted. Transferal of the yarn can be achieved by a deflector guide which is moved parallel to the spindle axis, or the winding guide itself can be so moved. The grooved roll is provided with a circumferential (non-helical) groove which aids in holding the yarn against traversing movement.
The problem of loose trailing ends has also been dealt with in German Patent No. 296,203 and French Patent No. 2,312,446. In the latter it has been proposed to position a movable bar intermediate the traverse guide and the package. The bar is moved into engagement with the yarn at the end of the winding sequence in a direction perpendicular to the spindle axis. The bar has a notch which captures the yarn and resists further helical winding of the yarn on the packages. As a result, the yarn is wound in relatively close order on the package to resist subsequent unraveling. Thus, the yarn is permitted to be oscillated by means of the traverse guide, e.g., a reciprocable slot or a grooved roll, while being restrained against traversing movement by a stationary notch immediately downstream of the traverse guide. Under those conditions, however, there may be a tendency for the yarn to be adversely affected. That is, at the extreme ends of its traversing or oscillatory travel, the yarn extends at a relative sharp angle around the traverse guide as it heads toward the stationary notch. Travel of the yarn through such an angle can result in a severe stressing of the yarn, imparting so-called "tension spikes" to the yarn which adversely affects the die absorbing characteristics of the yarn. Moreover, it is possible that the continuous traversing movement of the yarn upstream of the notch may cause the yarn to be prematurely dislodged from the notch.
It is, therefore, an object of the present invention to minimize or obviate problems of the type described above.
Another object is to wind a trailing yarn end in close order onto a package to prevent subsequent unraveling.
A further object is to provide such a close-order winding without imposing tension spikes in the yarn.
An additional object is to provide such close-order winding while resisting premature dislodgement of the yarn from a stationary yarn holder.
A further object is to provide a simplified, compact apparatus for ejecting a yarn from its traverse guide and holding the yarn for close-order winding on a passage.